Electrical protective device



April 5, 1949. w. G. TULLER ELECTRICAL PROTECTIVE DEVICE Filed NOV. 16, 1943 20 MVENTfi/fi Imam 6 77/440 Patented Apr. 5, 1949 UNITED STATES PATENT OFFICE ELECTRICAL PROTECTIVE DEVICE William G. Tuller, Watertown, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware 4 Claims.

This invention relates to dielectrically guided wave systems for the transmission and reception of electromagnetic waves of ultra high frequency, and more particularly to the construction and arrangement of the resonant cavity devices used in conjunction with such systems.

In guided wave transmission systems it is desirable, in certain instances, that a wave guide, such as a concentric line or a hollow wave guide, be utilized in both sending and receiving. Such systems are commonly called duplexing systems and are provided with one or more resonant cavities coupled to the Wave guide and fixed at proper intervals in relation to each other and to the transmitter. The resonant cavity devices are sometimes called TR boxes (transmission and receiving boxes) and also termed duplexing cavities. An example of such a system is disclosed in my copending application, Serial No. 511,456, filed November 23, 1943.

The duplexing cavities of such systems include a gaseous discharge device mounted Within the resonant cavity and having a pair of electrodes providing a spark gap. It is among the objects of the present invention to provide an improved construction for the TR boxes of such systems, and to provide a construction in which the gaseous discharge tube, providing the spark gap, may be readily assembled in or removed from the resonant cavity.

A further object of the invention is to provide a structure in which the TR. box is directly mounted upon the wave guide, preferably having a section integral therewith.

A further object of the invention resides in the provision of a resonant cavity coupled through an iris to the side of the wave guide with the resonant cavity positioned substantially tangential to the wave guide, whereby the distance between the cavity and the interior wall of the wave guide is reduced to a minimum, and whereby any discontinuity introduced when the spark gap breaks down will be substantially eliminated.

The above and other objects and features of the invention will be made fully apparent to those skilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawing in which:

Fig. 1 is a perspective view of a wave guide with a resonant cavity mounted thereon in accordance with the invention;

Fig. 2 shows a longitudinal section through the device of Fig. 1; and

Fig. 3 shows a transverse section taken on the line 3-3 of Fig. 2.

Referring to the drawing, reference numeral 1 indicates a Wave guide, which in the instance illustrated is a hollow tubular member. It Will be understood that the invention is equally applicable to wave guides of the type having a solid dielectric, and also the Wave guide may be of the concentric line type. A resonant cavity device 2 is formed in a plurality of sections, the innermost section 3 of which is directly attached to the wave guide I, and is preferably integrally united therewith, as by soldering. An outer section 4 is detachably mounted on the inner section 3 and defines, with the inner section, a cylindrical cavity 5 having an iris 5 openin into said wave guide. An ultra high frequency discharge device is mounted in the cavity, which device comprises an envelope 1 containing an ionizable gas and having a pair of the electrodes 3 and 9 projecting from diaphragms ID and H. The diaphragms H3 and I! are of relatively thin sheet metal of highly conductive material, such as copper, extending transversely through the tube and have outer peripheral portions extending beyond the circumference of the envelope '1. Lateral bores i2 and it of somewhat greated diameter than the diameter of the cylindrical cavity 5 are provided in the block formed by the sections 3 and t forming a somewhat enlarged continuation of said cylindrical cavity. The diaphragms It and H are of greater diameter than the diameter of the cylindrical surface of the cavity 5 having substantially the same diameter as the internal diameter of bores i2 and I3. A pair of clamping sleeves l4 and 15, extending through the lateral bores 52 and i3, clamp the peripheral edges of the diaphragms H3 and H against shoulders E5 and ll formed at the juncture of the bores l2 and i3 and the cylindrical cavity 5. Knurled nuts l8 and 29, having internal screw threads adapted to coact with external'screw threads upon annular bosses 20 and El projecting from the side walls of the sections 3 and 4, are provided with internal shoulders adapted to bear against external shoulders at the outer ends of the clamping sleeves I4 and 5 to securely clamp the peripheral portions of the diaphra-gms it and H against the shoulders i5 and I l.

A tuning pin 22 is adjustably mounted in a supporting block 23, which block may be suitably attached to the wave guide I, as for example by soldering. The tuning pin 22 is adapted to be longitudinally adjusted in a bore-2A opening into the cavity and may be locked in the adjusted position by means of a locking nut 25. A second. tuning pin 26 is adjustably mounted in a threaded bore 21 upon the diametrically opposite side of the box and is adapted to be locked in an adjusted position by a locking nut 28. The wave guide 5 may be provided with coupling screws 29 for coupling the section I to other sections of the wave guide.

It will be observed that in the above described construction the duplexing device 2 is formed in two sections with the joint between the sections splitting the cavity 5 at about the center line thereof. One half of each of the bosses 2t and 2| is formed on each of the two sections. With the upper section removed, the device may be readily assembled by placing the tube 7 in position in the lower section 3 wherein it will be properly centered by the lower halves of shoulders Hi and i1 coacting with the diaphragms 9 and H3. The upper section d may then be placed over the lower section, being guided into position by centering pins 38. To insure that the threads on the two halves of the annular bosses 2! will match accurately, the sections 3 and i may be secured together in intimate contact along the opposing faces thereof by means of screws 3!. The sleeves I l and !5 are then inserted in the bores 32 and i3, and nuts l8 and 39 are threaded on the bosses 2B and 21. The nuts force the sleeves l4 and I5 against the peripheral edges of the diaphragms l6 and H and thus clamp the diaphragms in intimate contact with the shoulders 56 and H. The diaphragms IE3 and l l thus form closures for the ends of cavities 5 leaving the cavity completely enclosed except for the iris 6. Since the electrodes 8 and 9 project from the centers of the diaphragms l8 and l l', the discharge gap or spark gap formed thereby lies in, or approximately in, the center line of the cavity. Preferably the cavity 5 is positioned so that the projection of its interior cylindrical surface at the iris 6 is substantially tangent to the projection of the internal wall of the wave guide i at said this iris opening. By substantially tangent, I mean that said interior surface of the cavity should not be spaced a distance greater than from the projection of the interior wall of the wave guide at the iris opening, where A is the wave length of the transmission system with which the device is associated. 3

I have found that when so disposed the discontinuity which is introduced upon break down of the spark gap where the cavity is positioned otherwise is substantially eliminated. Accordingly, when the cavity is cylindrical, as shown, the distance between the center line of the cavity and the internal wall of the wave guide is approximately equal to the radius of the cavity.

It will be understood that the geometry of the cavity may vary considerably from the cylindrical form shown. For example, the cavity may be rectangular in cross-section, in which case one of the bounding surfaces of the cavity may have an area extending parallel to an interior surface of the wave guide, in which case the tangential relation desired will be obtained if the two parallel surfaces of the cavity and the guide are not more than apart at the iris opening.

In operation, it will be understood that when the system with which the device is associated is transmitting, the discharge gap or spark gap provided by the opposed electrodes 8 and 9 will break down, permitting the waves of high energy to pass through the wave guide substantially unimpeded. When waves of lower energy are passing through the system, as when the same is functioning as a receiver, the gap does not break down, resulting, in effect, in an open circuit between the antenna system and the transmitter, and the received energy may be transferred to a suitable receiver in any manner known in the art. One suitable transmission and receiving system with which the device may be associated is disclosed in my copending application, Serial No. 511,456 filed November 23, 1943. Other applications of the invention in various transmission and receiving systems will be obvious to those skilled in the art.

While there has been herein disclosed one i1- lustrative and preferred embodiment of the invention, other embodiments within the scope of the appended claims will be aparent to those skilled in the art from a consideration of the form shown and from the teachings hereof.

What is claimed is:

1. In a guided wave system, a tubular wave guide, a duplexing device mounted on said wave guide, said device comprising a section integral with said wave guide, and a section detachably mounted on said first section and defining therewith a duplexing cavity, said cavity having a substantially cylindrical internal surface positioned substantially tangential to the wall of said wave guide, and having an opening between said wave guide and cavity therethrough, a discharge tube in said cavity, a pair of metallic diaphragms extending transversely through said tube and having projecting portions in electrical contact with said cylindrical surface.

2. In a guided wave system, a tubular wave guide, a duplexing device mounted on said wave guide exteriorly thereof, said device comprising a section mounted on said wave guide having an opening therebetween and defining one-half of the circumferential walls of a cavity resonator, and a section detachably mounted on said first section and defining the other half of the circumferential walls of said cavity resonator, a discharge tube in said cavity and a pair of electrodes in said tube electrically connected to said walls of said cavity and providing a spark gap.

3. In a guided wave system, a tubular wave guide, a duplexing device mounted on said wave guide exteriorly thereof, said device comprising a section mounted on said wave guide defining onehalf of the circumferential walls of a cavity resonator, and a second section detachably mounted on said first section and defining the other half of the circumferential walls of said cavity resonator, a gaseous discharge device in said cavity having a pair of electrodes electrically connected through the walls of said cavity and providing a spark gap, said cavity having a bounding surface in said first section positioned substantially tangential to the wall of said wave guide, and having an opening between said wave guide and cavity therethrough.

4. In a guided wave system, a tubular wave guide, a duplexing device mounted on said wave guide exteriorly thereof, said device comprising a section mounted on said wave guide defining onehalf of the circumferential walls of a cavity resonator, and a second section detachably mounted on said first section and defining the other half of the circumferential walls of said cavity resonator, said cavity having a bounding surface in said first section positioned substantially tangential to the wall of said wave guide, and having an opening between said wave guide and cavity therethrough, a discharge tube removably mounted between said sections, and means associated with said tube providing the end walls of said cavity.

WILLIAM G. TULLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,241,119 Dallenoach May 6, 1941 2,263,648 Salzberg Nov. 25, 1941 2,308,523 Llewellyn Jan. 19, 1943 2,396,044 Fox Mar. 5, 1946 2,412,751 Rochester Dec. 17, 1946 2,413,171 Clifford Dec. 24, 1946 2,415,962 Okress Feb. 18, 1947 2,446,982 Pound Aug. 10, 1948 

